Laminated core for electrical apparatus



(No Model.)

A. SOHMID.

LAMINATED GORE FOR ELECTRICAL APPARATUS.

No. 406,776. Patented July 9, 1889.

WITNESSES:

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UNITED STATES PATENT ,OFFICE.

ALBERT SCHMID, OF ALLEGHENY, ASSIGNOR TO THE \VESTINGHOUSE ELEC- TRIC COMPANY, OF PITTSBURG, PENNSYLVANIA.

LAMINATED CORE FOR ELECTRICAL APPARATUS.

SPECIFICATION forming part of Letters Patent No. 406,776, dated July 9, 1889. Application filed November 6, 1888. Serial No. 290,150. (No model.)-

To all whom it may concern: of soft iron, from which the laminze are after Be it known that I, ALBERT SOHMID, a citiward stamped. In this way very thin insuzen of the Republic of Switzerland, residing lation may be obtained and the proportion of in Allegheny, in the county of Allegheny and iron in the core correspondingly increased;

State of Pennsylvania, have invented a new but even with this form of insulation the non- 5 5 and useful Improvement in Laminated Cores conducting material is found to occupy about for Electrical Apparatus, (Case No. 260,) of one-sixth as much space as the iron. Another. which the following is a specification. difficulty sometimes encountered in this con- My invention relates to certain improvestruction is that the operation of stamping IO ments in the manufacture of cores for electhe plates forms a burr along the out edges, 60 trical apparatus-such, for instance, as the and when the plates are placed together the cores of electric inductoriums or converters, burrs are liable to pierce through the sheets the cores of armatures for electric generators of paper, and thus destroy to a greater or less and motors, and other similar apparatus. extent the insulation between the different I 5 It has been found in practice that cores for plates.

electrical apparatus, which are subjected to a The object of the present invention thererapid change of magnetic condition, are more fore is to overcome these difficulties and to efficient and less liable to become heated when reduce to a minimum the spaces occupied by built of electrically-insulated laminse of soft the insulation, and at the same time to proiron than when made solid. This is due to vide a method of manufacturing the core 70 the fact that in solid cores the electric curwhich will secure the required insulation berents generated therein circulate within the tween the laminae, and shall also cheapen same. Such currents, while of comparatively and improve the construction of the'core. low electro-motive force, are of considerable The invention consists in first stamping quantity, and are liable to heat the core and from sheets of magnetizable material-such, 7 5 render it less efficient. The use of laminated for instance, as ironplates of the required cores has therefore become quite universal. size and form, from which to build up the In some instances the adjacent laminae have core, then subjecting the plates'to an annealbeen held apart by narrow'washers, leaving ing process,whieh is carried to such an extent 3o narrow air-spaces between the laminae. In that a thin film of oxide is formed over their 80 other instances thin sheets of paper, fiber, or entire surfaces, and over, also, the burrs or other non-conducting material are placed berough edges produced by the stamping protween the laminae of soft iron. cess, and afterward building up the core by It is usually desirable that the mass of iron placing such plates side by side.

3 5 in proximity to the coils of wire applied to a The annealing process is carried on in the 85 core should be as great as possible. The presfollowing manner: The plates are arranged ence of the insulation bet-ween the laininze in small piles in a suitable annealing-box. lessens somewhat the amount of iron which The box is then placed in a furnace and gradis contained in a core of given size, and to a ually heated. This step, in practice, usually 40 corresponding extent tends to detract from occupies from six to twelve hours. \Vhen the 0 the efficiency of the core. For this reason, it proper temperature has been reached, it is is desirable that the insulation between the kept approximately constant for a sufficient laminae should be as thinas possible; The time to produce the required effects. This use of washers or thin plates of insulating mamay vary in different in stances; but I usually 5 terial is therefore objectionable, because it continue to so heattheplates for abouttwelve 5 requires a considerable separation of the suchours. They are then allowed to cool graducessive plates. ally, the heat being gradually lessened. This Another plan is to obtain the insulation by may occupy a somewhat greater length of pasting very thin sheets ofpaper or other intime-say from twelve to twenty-four hours.

sulating material to one surface of the sheets The gradual cooling secures thoroughly-an- ICO nealed soft plates. After this treatment the plates are found to be coated with a dark film or very thin scale. This scale consists chiefly of magnetic oxide. It is such a poor conductor of electricity as in effect to amount to an insulator, and at the same time it is more or less magnetic, so that it serves, when the plates are placed together, not only to insulate them from each other, but also as a magnetizable material for the core, thus com bining two desirable qualities. At the same time the insulation is extremely thin, and therefore allows the plates themselves to be brought into very close proximity. The thickness of the scale or film is found to be about two ten-thousandths of an inch upon each surface, so that the core consists almost entirely of magnetizable material, and the plates themselves are separated the smallest possible distance.

The oxide is very firmly attached to the surfaces of the plates and can only be removed by attrition, so that the plates may be handied without special care and without endangering the insulation.

It is desirable that the metal should be as soft as possible. As already stated, the annealing process has the effect of removing whatever temper may have been given to or remain in it, thus softening it and satisfying this requirement. The metal cannot in practice be so perfectly annealed while in the form of the large sheets from which the plates are stamped, as it is impossible to heat and cool them evenly; neither can it be thoroughly annealed before it is rolled into sheets, and the subsequent operation of rolling tends to harden it.

In the accompanying drawings, Figure 1 is a side view of a plate employed in building certain forms of converters, such as described, for instance, in Letters Patent No. 360,317, issued July 12, 1887, upon an application filed by me. Fig. 2 is a plan of a converter having a core of the character described. Fig. 3 illustrates an armature-plate, and Fig. at an armature-core composed of such plates.

Referring to Figs. 1 and 2,A represents the core of the converter of the construction which it is preferred to employ, and O G the primary and secondary coils, respectively. The converter may, however, be constructed with a single coil, a portion of the length being designed to be connected in one circuit and a portion in another; or a single coil may be connected entirely in one circuit. The core is composed of thin sheets or plates to, of magnetizable materialsuch, for example, as soft iron. In preparing these plates rectangular plates are stamped with two holes 0 c and these holes are preferably of a rectangular shape and of such size as to receive the coils of wire. Each hole (2 e is cut open atf f These cuts f f may converge, as shown in the figure. After the plates have been properly stamped they are placed in suitable vessels and gradually heated to a very high temperature. They are kept at such temperature a proper length of time and then allowed to cool slowly. This step in the process has the double eifect of thoroughly annealing and softening the metal and coating the surfaces with a thin film of magnetic oxide. This film also covers the edges and reduces the burrs produced by the stamping, covering them with an insulating material. In this manner the entire surface of each plate is sufliciently insulated to pre vent any considerable circulation of Foucault or eddy currents in the core. The plates are then placed one against another, their central tongues being inserted within the coils in the same general manner as described in the patent before referred to, alternate plates being preferably inserted from opposite sides. The manner of building up the core and the shapes of the plates may, however, be materially varied without departing from the spirit of my invention.

Figs. 3 and 1 illustrate the construction of the cores of armatures for electric machines. The plates A'are stamped as before, the shape and form being suited to the particular form of armature desired. They are then annealed and thereby softened, and coated by a film of insulating oxide, and afterward placed to gether side by side to form the complete armature-core. (Shown in Fig. 4..)

I desire it to be understood that I do not limit my claims to the particular forms of cores herein described, nor to the precise periods of heating and cooling, nor to the precise methods of annealing set forth in the specification, but present them. as being best suited to illustrate and disclose my invention.

In another application, Serial No. 310,590, filed May 13, 1889, the method of forming cores herein described is set forth and claimed.

I claim as my invention 1. A core for electrical apparatus, consisting of thin stamped plates of magnetizable material placed side by side and intervening layers or laminae of electrically-insulating magnetic oxide formed upon and covering the entire surfaces and edges of the plates.

2. A core for electrical apparatus, composed of thin stamped plates of magnetizable material and intervening strata of nonelectrieconducting oxide formed upon the surfaces of such plates and covering the edges and burrs thereof.

A core for electrical apparatus, consisting of stamped plates of magnetizable material placed side by side and in contact with each other, said plates being annealed after being stamped, whereby their entire surfaces and edges are coated by an oxide.

at. A core for electrical apparatus, consisting of alternate layers of magnetizable material and magnetic oxide formed by anncaling after the plates are stamped.

5. A core for electrical apparatus, consist- IIO ing of alternate layers of magnetizahle ma- In testimony whereof I have hereunto subterial and magnetic oxide, the latter being scribed my name this 5th day of November, formed in layers upon the surfaces of the A. D. 1888.

plates and covering the edges and burrs.

5 6. A core for electric converters, consisting ALBERT SCHMID.

of annealed plates of magnetizable material placed side by side and intervening laminae \Vitnesses: of insulating oxide formed upon the surfaces CHARLES A. TERRY, of the plates and covering the edges thereof, C. O. YVOLFE.

10 in combination with coils of insulated wire. 

